Brazilian river Rio Doce, most important river in the state of Minas Gerais, declared officially dead due to the dams burst in the city of Mariana.
The disaster that happened in the city of Mariana, in the state of Minas Gerais, was unprecedented, with at least 9 people dead and 18 people disappeared counted so far. Furthermore, it is noticed that the environmental disaster caused by the dams burst is already putting an end to Rio Doce, the most important river of Minas Gerais. Specialists already declare it officialy dead. Laboratory analysis, ordered after the disaster, found particles of heavy metals such as lead, aluminum, iron, barium, copper, boron and mercury in the river’s water. Luciano Magalhães, director of SAAE (Autonomous Service Of Water And Sewer), organ responsible for the analysis, claimed that “it seems they’ve thrown the entire periodic table” into the river. According to him, the water has no more use at all and it’s improper for irrigation and animal and human consumption.
In addition to those heavy metals, the mud’s mere force has already devastated the river’s biodiversity forever. Environmentalists don’t discard the possibility that entire endemic species have been extinct by the mud. The ammount of mud is so huge that the river had its natural course blocked, which made it lose force and form little lakes that are also not going to last long, given that, in addition to the minerals, sewers, pesticides and agrochemicals are also being carried by the waters.
Fishermen of the region created the Noah’s Ark Operation to act in areas of Rio Doce’s hydrographic basins that haven’t been hit by the flood yet, using boxes, buckets, and plastic sheets to transfer fish to lakes with clean water. When visiting the places affected by the burst, Brazilian president Dilma Rousseff declared that the preliminary fine Samarco (mining company responsible for the dams) must pay for the environmental damage is going to be around R$250 million (US$65.01 million).
A document emitted by Minas Gerais’s Public Ministry, issued in October 2013 during the process of renewal of the concession license for Samarco, reveals that there were risks of disruption of the city’s dams. According to the text, the situation of the structure was not recommended because of possible erosion (such as cracks or openings) that could destabilize the dam of waste coming from the mining process.
“The waste dump [ground layer] requires low humidity and good drainage”, conditions that, according to the justice promoter Carlos Eduardo Ferreira Pinto, who analysed the report, are not found in dams like those that broke in Mariana, since they require high humidity to function as a water reservoir.
In this type of structures, there are infiltrations - that must be properly drained. The problem is when the drainage system of the infiltrated water fails and causes internal erosion in the dam.
The prosecutor has stated that a dam burst of this magnitude doesn’t happen by accident, even if there is a natural cause event. “What happened was negligence in the company’s operation, and that is what we are investigating”, Pinto said.
However, Hernani Mota de Lima, mine engineering professor at the Federal University of Ouro Preto (UFOP), has claimed that the climatic conditions of the region contradict the hypothesis of the Prosecutor.
“Today we are in a period of drought. Thus, the structure has no contact with moisture, which contradicts the 2013 report”, he describes. "But we must wait for the expert opinion”.
So far, there is no technical analysis stating the causes of the disaster.
Sources (in portuguese): x, x
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